temperature

[wēn dù]

physical quantity

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Temperature refers to the degree of cold and hot of objects physical quantity In microcosm, it is an object Molecular thermal motion The intensity of. The temperature can only be determined by some properties of the object that change with temperature Indirect measurement , used to measurement The scale of object temperature value is called Temperature scale 。

It specifies the starting point (zero point) of temperature reading and the basic unit of temperature measurement. In SI units Thermodynamic temperature scale （K）。 Other temperature scales widely used internationally are Fahrenheit scale （°F）、 Celsius scale (° C) and International practical temperature scale 。

from Theory of molecular motion From the point of view, temperature is the average of molecular motion of objects kinetic energy Logo of. Temperature is the collective expression of the thermal movement of a large number of molecules, with statistical significance. For individual molecules, temperature is meaningless. The degree of heat and cold measured on one of several arbitrary scales according to an observable phenomenon (such as the expansion of a mercury column).

Chinese name: temperature
Foreign name: temperature
Pinyin: wēn dù

Role: A physical quantity that represents the degree of cooling and heating of an object
Abbreviations: T
International unit: Kelvin

catalog

one Basic meaning
▪ air temperature
▪ Measurement of surface air temperature
two Citation explanation
three Scale level
▪ Kelvin unit
▪ Fahrenheit scale
▪ Celsius scale
▪ Relationship between the two

Basic meaning

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Particle collider

The degree of heat and cold measured on one of several arbitrary scales according to an observable phenomenon (such as the expansion of a mercury column). Temperature is a form of intermolecular translational kinetic energy in an object. The faster the molecules move, that is, the higher the temperature, the hotter the object; The slower the molecules move, that is, the lower the temperature, the colder the object. from Theory of molecular motion From the point of view, the temperature is the sign of the average kinetic energy of the molecular motion of the object, and the temperature is Molecular thermal motion The collective performance of is statistically significant.

(When the temperature is high enough to burn the oxygen in the air into flame to a certain extent, heat transfer can lead to material melting and melting. When the temperature is high enough, material (mass) and energy will be destroyed; When the temperature is low to a certain extent, it can be mixed with water or air or water in the body (blood) freezing Ice formation transfers cold, and freezing can lead to substances fragmentation It is extremely cold and can shatter material, mass and energy. Anything that endangers life can change the moving (moving) speed of objects

For vacuum, the temperature is ambient temperature , is the object in the Vacuum environment The average kinetic energy between molecules in a body. The temperature of objects is different in different vacuums under the radiation of different heat sources. This phenomenon is called vacuum ambient temperature. For example, objects in space near the sun have higher temperatures; The object is far away from the sun in space, on the contrary, the temperature is lower. This is the impact of solar radiation on the space environment temperature.

air temperature

atmosphere The temperature of medium gas is the temperature, which is a common term in meteorology. It is directly affected by sunlight: the more sunlight, the higher the temperature. China Celsius scale (℃). The ground temperature mentioned by the meteorological department refers to the temperature in the leaf box at about 1.5m high ground level.

Measurement of surface air temperature

meteorological observatory The main instrument used by the station to measure the air temperature near the ground is equipped with Mercury or alcohol Glass tube thermometer. Since the thermometer itself has a greater ability to absorb solar heat than air, the reading indicated by sunning is often higher than the actual temperature of the surrounding air, so it is necessary to measure the temperature near the ground air temperature The thermometer is usually placed in a louver box ventilated on all sides about 1.5m from the ground.

Citation explanation

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1. The degree of cold and hot. Bingxin's Aunt Fen: "You will always be a pot of flowers in the greenhouse. You will be delicate and open under the uniform temperature without wind and rain." Selected Novels, 1981, Issue 8: "Little brother, you can't just talk about style, forget the temperature, and you should wear thick clothes."

2. It refers to heat. Lao She's Divorce No. 20: "It's not good to visit relatives and friends, especially fat people, in summer. But Mrs. Wu has to go out to look for relatives and ask friends, as if only to increase the temperature in someone's house."^[1]

Scale level

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Kelvin unit

high temperature

with Absolute zero The temperature used as the starting point for calculation. Soon water Three phase point The temperature of is accurately defined as the temperature obtained after 273.16K, which was also called absolute temperature in the past. Kelvin temperature The common symbol K, whose unit is Kelvin, is defined as 1/273.16 of the triple point temperature of water. Kelvin temperature and what people are used to Celsius temperature The difference is a constant 273.15, that is,=+273.15 (the symbol of Celsius temperature).^[2]

For example, the triple point temperature of water expressed in Celsius is 0.01 ℃, while Kelvin temperature Means 273.16K. The difference between Kelvin temperature and Celsius temperature is only that the starting point of the calculated temperature is different, that is, the zero point is different, and there is one difference between them constant , can be converted to each other. The difference between the two cannot be compared with Thermodynamic temperature It is confused with the difference between international practical temperature scale and temperature, and the difference between the latter two is the difference in definition. Thermodynamic temperature can be expressed as Kelvin temperature; Similarly, the international practical temperature scale temperature can also be expressed as Kelvin temperature. Of course, they can also be expressed in Celsius. So 1 ℃=274.15K, 0 ℃=273.15K.

Fahrenheit scale

Fahrenheit degree Fahrenheit and Centigrade are units used to measure temperature. Many countries in the world, including China, use Celsius, while the United States and some other English speaking countries use Fahrenheit and less Celsius.

It is named after its inventor Gabriel D. Fahrenheit (1681-1736) Freezing point It is 32 ° F and the boiling point is 211.9532 ° F. In 1714, Fahrenheit, a German, made glass with mercury as the temperature measuring medium Mercury thermometer , select ammonium chloride The temperature of the mixture with ice water is zero of the thermometer, and the human body temperature is 100 degrees of the thermometer Volumetric expansion The distance is divided into 100 parts, each of which is 1 ° F and recorded as "1 ° F". Most countries in the world, including China, use Celsius; Only five countries in the world use Fahrenheit, including the Bahamas, Belize, the British Cayman Islands, Palau, the United States of America and other dependent territories (Puerto Rico, Guam, the United States Virgin Islands).

Celsius scale

Its inventor is Anders Celsius (1701-1744), whose freezing point is 0 ℃ and boiling point is 99.974 ℃. In 1740, the Swedish Celsius proposed that Standard atmospheric pressure Next, put Ice water mixture The temperature of is specified as 0 ℃, and the boiling temperature of water is specified as 99.974 ℃. The glass mercury thermometer is graduated according to the two fixed temperature points of water. Two points are divided into 100 equal parts, each of which is called 1 ℃. It is recorded as 1 ℃. Celsius temperature has been included International System of Units 。 In physics, the temperature of Celsius is expressed as t, Absolute temperature (Unit: Kelvin) is expressed as T, and the definition of Celsius temperature is t=T-273.15. Celsius means that the temperature of Celsius will replace Kelvin A special name of, 1K=1 ℃ in numerical value.

Relationship between the two

Celsius temperature and fahrenheit Relationship between: T ℉=1.8t ℃+32 (t is the temperature in Celsius, T is the temperature in Fahrenheit)

Celsius temperature and Kelvin temperature Relationship between: ° K=℃+273.15

Temperature under different temperature scales

Temperature scale	Absolute zero	Freezing point of water at standard atmospheric pressure	Normal body temperature	Boiling point of water at standard atmospheric pressure
Open temperature scale	0.00K	273.15K	309.95K	373.124K
Celsius scale	-273.15℃	0.00℃	36.80℃	99.974℃
Fahrenheit scale	-459.67°F	32.00°F	98.24°F	211.9532°F
Richter scale	-218.52°Ré	0.00°Ré	29.44°Ré	79.9792°Ré
Rankin temperature scale	0.00R	491.67R	557.91R	671.6232R

Temperature scale classification

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In order to measure the temperature quantitatively, the numerical expression method of temperature must be determined first, and then thermometer Scale. The numerical representation of temperature is called the temperature scale. The so-called numerical representation includes two aspects: one is the basis for determining the temperature value; The second is the scaling method. Specifically, it includes the following three elements:

First, select the temperature measurement material and its temperature measurement attribute, which is represented by numerical value, i.e. the temperature measurement parameter X of a certain material (such as platinum resistance; thermocouple Thermoelectric electromotive force Etc.)

Second, determine the relationship between temperature measurement parameters and temperature (before establishing any temperature scale, this relationship is only a hypothetical relationship based on certain experience).

For example, determined as linear relationship

t=aX+b　（2.1）

(2.1) A and b in the formula need to be determined by the values of the two standard temperature points taken; Another example is to determine that the temperature is proportional to the temperature measurement parameters

T=aX　（2.2）

In the formula, a can be determined by only one standard temperature point.

Third, determine the standard temperature point and specify its value, which is the scaling method.

The above three elements actually include five aspects:

① Thermometric quality;

② Temperature measurement properties (temperature measurement parameters);

③ The relationship between temperature and temperature measurement parameters;

④ Standard temperature point;

⑤ The value of the standard temperature point.

Any temperature scale has definite contents in these five aspects (except that the thermodynamic temperature scale does not involve thermometers), and changing any one of them becomes another temperature scale. However, the name of a temperature scale cannot express all the factors that establish the temperature scale. In addition, some books do not strictly follow the principle of conceptual division when introducing the types of temperature scales (for example, each division can only be based on the same standard), but juxtapose different temperature scales divided by different standards, This makes it easy to confuse the temperature scales; What are the differences between various temperature scales and what are the relationships between them.

The classification of various temperature scales is as follows:

Scale method

(i.e. the third article of the three elements) are divided into:

① Fahrenheit scale

It was established by Fahrenheit (1686-1736, Netherlands) in 1714. He initially stipulated ammonium chloride 0 ° F with ice; Human body temperature is 100 ° F. Later, it was specified that the mixture of pure water and ice in standard state was 32 ° F; The boiling point of water is 211.9532 ° F. The two standard points are evenly divided into 180 equal parts, each of which is 1 ° F.

② Richter scale

It was founded by Reaumur (1685-1757, France) in 1740. He set the freezing point of water as 0 ° R; Change the volume of alcohol by one thousandth to 1 ° R. Thus, the boiling point of water is 79.9792 ° R.

③ Celsius scale

It was founded by Celsius (1710-1744, Sweden) in 1742. Initially, he set the freezing point of water as 0 ° C; The boiling point of water was set at 99.974 ° C. Later, he accepted the suggestion of Swedish scientist Lin Lie and exchanged the values of the two temperature points. 1960 International Conference on Metrology A new definition of the Celsius temperature scale is made, which is defined by Thermodynamic temperature scale Export. The definition of Celsius temperature (symbol t) is t/° C=T/K-273.15.

④ Kelvin scale

It was founded by Lord Kelvin (1824-1907, England) in 1848. The 1954 International Conference on Metrology stipulated that the temperature of the triple point of water was 273.16K. This value is specified for historical reasons.

I. In order to make the temperature interval per degree of Kelvin temperature scale equal to the interval per degree of Celsius scale method established and widely used;

II. Press Ideal gas temperature scale , the ideal gas's Thermal expansion rate 1/273.15. It is thus determined that - 273.15 ° C is the zero of absolute temperature, and the absolute temperature of freezing point is 273.15K;

III. When the standard temperature point is changed from the freezing point of water to the three-phase point of water (the difference is 0.01 ° C), the temperature of the three-phase point of water determined according to the ideal gas temperature scale is 273.16K.

According to temperature measurement

It includes the temperature measurement quality, the temperature measurement parameter X and its relationship with temperature.

① Empirical temperature scale

The temperature scale, which is determined by the relationship between a specific temperature measuring property of a specific temperature measuring material and temperature, is often called a thermometer. as Mercury thermometer ， Alcohol thermometer ， Platinum resistance thermometer , constant volume hydrogen thermometer, etc.

Generally speaking, according to the same scale method (such as Kelvin), but using the same temperature measurement parameter with different temperature measurement materials (such as copper constantan thermocouple) Thermoelectric electromotive force Is proportional to the temperature T; The thermoelectric electromotive force of copper steel thermocouple is proportional to the temperature T); Or different temperature measurement parameters of the same substance (for example, the volume of mercury is proportional to the temperature T; the resistance of mercury is proportional to T); Or different thermometers made of different temperature scales established by different temperature measuring materials and different temperature measuring parameters (such as copper constantan Kelvin scale method and platinum resistance Kelvin scale method), when measuring the temperature of the same system to be measured and the same equilibrium state, their readings are not strictly consistent. This is because the relationship between different properties of different substances and temperature is not the same.

Therefore, we establish an empirical temperature scale by stipulating that the temperature measurement property of a certain temperature measuring substance is proportional to the temperature change, and then use the thermometer made according to this temperature scale to measure the relationship between other measurement properties and the temperature change, and it is generally no longer proportional. However, when we establish different temperature scales, we stipulate that they are proportional to temperature. Each thermometer made in this way will inevitably cause a difference in reading. For example, copper constantan (Kelvin scale method) thermometers and rtd (Kelvin scale method) thermometer, and measure the normal boiling point of nitrogen at the same time. The reading of the former is 32K and that of the latter is 54.5K.

This problem is a serious one for measurement. In order to find an ideal standard temperature scale (no difference in readings due to different temperature measurement quality and parameters), it has gone through a long process from empirical temperature scale to semi theoretical temperature scale to theoretical temperature scale.

② Semi theoretical temperature scale Ideal gas temperature scale

The establishment of ideal gas temperature scale is introduced in detail in almost all textbooks of general physics, so it will not be repeated here.

ideal gas The advantage of the temperature scale over the empirical temperature scale is that it has nothing to do with any particular property of any gas. No matter what kind of gas is used, the temperature value determined by them is the same when the pressure is extrapolated to zero. However, the ideal gas temperature scale also depends on the commonness of gases after all, and is not applicable to extremely low temperatures (helium boiling point below 1K under the vapor pressure of 1.01 × 10Pa) and high temperatures (above 1000 ° C). Moreover, the ideal gas temperature scale is not convenient enough in specific operation.

③ Theoretical temperature scale thermodynamic temperature scale

We will not repeat the process of establishing the thermodynamic temperature scale here. As we all know, in the thermodynamic temperature scale, heat Q plays the role of temperature measurement parameter, but the ratio Q1/Q2 (Q1 is the heat absorbed by the reversible machine from the high temperature heat source; Q2 is the heat released by the reversible machine to the low temperature heat source) does not depend on the characteristics of any substance. Therefore, the thermodynamic temperature scale is independent of the temperature measuring material.

Of course, any kind of temperature scale must be a combination of some measurement basis and some scaling method. Generally speaking, any scaling method can be used for certain temperature measurement parameters of different thermometers. Such as mercury centigrade thermometer, alcohol centigrade thermometer; Different scaling methods can also be used for any temperature measurement parameter. For example, ideal gas Kelvin temperature scale, ideal gas Celsius temperature scale. However, for the thermodynamic temperature scale with heat Q as the temperature measurement parameter, the scaling method only takes Kelvin scaling method, which is based on The second law of thermodynamics This is the fundamental difference between it and other temperature scales.

④ Agreed temperature scale

Thermodynamic temperature scale is a temperature scale that does not depend on any specific temperature measuring material and its temperature measuring properties, and is of course the most ideal temperature scale. However, we cannot build a reversible heat engine, so we cannot measure the heat absorbed by the reversible heat engine from a high temperature heat source heat source The ratio of heat released. But when it is theoretically proved that the Kelvin scale method is used, the temperature measured according to the thermodynamic temperature scale is Ideal gas temperature scale When the measured temperature is the same, the ideal gas temperature scale can be used to achieve the thermodynamic temperature scale.

However, due to the complexity of the temperature measurement program by the ideal gas temperature scale, it is extremely inconvenient and fast, and has a certain scope of application. The International Conference on Metrology has held many meetings to discuss the development of an international practical temperature scale, so that temperature can be measured simply, conveniently and correctly. In 1927, the first international practical temperature scale (ITS-27) was drawn up. Since then, with the continuous development of science and technology, the International Practical Temperature Scale has been improved by the revision of the International Metrology Conferences in 1948, 1960 and 1990. The basic idea of the international practical temperature scale is to divide the temperature range into several regions, and each region uses a thermometer that is easy to operate. But their scales are approximated by thermodynamic temperature scale, that is, there are different standard formulas in different temperature regions. In this way, the scale on the thermometer is not necessarily uniform, but the measured temperature is as close as possible Thermodynamic temperature 。 With the improvement of science and technology, the protocol temperature scale is constantly improved, so as to narrow the gap between the international practical temperature scale and the thermodynamic temperature scale. For example, more accurately determine the temperature of the standard temperature point; Modified interpolation formula; Improve the reference thermometer, etc.

90 International Temperature Scale

Code: ITS-90 (International Temperature Scale of 1990)

The key points are as follows:

① The thermodynamic temperature scale is taken as the basic temperature scale.

② Thermodynamic temperature Represented by the symbol T, the unit is Kelvin , short for open, symbol K.

③ The value of 1K is defined as 1/273.16 of the thermodynamic temperature of the triple point of water.

④ The centigrade temperature (symbol is t) is derived from the thermodynamic temperature, which is defined as t=T-273.15. The unit of temperature of Celsius is called Celsius, the symbol is ° C, and its size is the same as Kelvin.

⑤ Divide four temperature segments and specify the reference thermometer for each temperature segment:

Ⅰ、0.65 K—5.0 K。 In this temperature range, the reference thermometer is He vapor pressure thermometer.

II. 3.0 K-24.5561 K (three-phase point of neon). In this temperature range, the reference thermometer is He fixed gas thermometer.

Ⅲ, 13.8033 K (three-phase point of equilibrium hydrogen) - 1234.93 K (silver freezing point ）。 In this temperature range, the reference thermometer is Platinum resistance thermometer 。

Ⅳ. Above 1234.94 K, according to Planck radiation law definition.

Seventeen standard temperature points defined in ITS-90 are listed in the table below.

Substance state	temperature
Substance state	T90/K	t90/℃
Boiling point of helium at atmospheric pressure	3~5	-270.15～-268.15
Three phase point of equilibrium hydrogen	thirteen point eight zero three three	-259.3467
Boiling point of equilibrium hydrogen at 25/26 standard atmospheric pressure	≈17	≈-256.15
Boiling point of equilibrium hydrogen at one standard atmospheric pressure	≈20.3	≈252.85
neon Three phase point	twenty-four point five five six one	-248.5939
Oxygen triple point	fifty-four point three five eight four	-218.7916
argon Three phase point	eighty-three point eight zero five eight	-189.3442
mercury Three phase point	two hundred and thirty-four point three one five six	-38.8344
Three phase point of water	two hundred and seventy-three point one six	0．01
gallium melting point	three hundred and two point nine one four six	twenty-nine point seven six four six
Indium freezing point	four hundred and twenty-nine point seven four eight five	one hundred and fifty-six point five nine eight five
Tin freezing point	five hundred and five point zero seven eight	two hundred and thirty-one point nine two eight
Freezing point of zinc	six hundred and ninety-two point six seven seven	four hundred and nineteen point five two seven
Aluminum freezing point	nine hundred and thirty-three point four seven three	six hundred and sixty point three two three
Silver freezing point	one thousand two hundred and thirty-four point nine three	nine hundred and sixty-one point seven eight
Gold freezing point	one thousand three hundred and thirty-seven point three three	one thousand and sixty-four point one eight
Copper freezing point	one thousand three hundred and fifty-seven point seven seven	one thousand and eighty-four point six two

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Contact thermometry

Temperature measuring instrument

Contact thermometry It is characterized by direct contact between the temperature measuring element and the measured object, and sufficient communication between them heat exchange At last, the thermal balance is reached. At this time, the measurement value of a physical parameter of the temperature sensing element represents the temperature value of the measured object. The advantage of this method is intuitive and reliable, but the disadvantage is that the temperature sensor affects the measured Temperature field The distribution of, poor contact, etc. will bring measurement errors. In addition, too high temperature and corrosive media will adversely affect the performance and life of temperature sensing elements influence 。^[3]

Non-contact thermometry

The non-contact temperature measurement method is characterized by that the temperature sensing element does not contact the measured object, but conducts heat exchange through radiation, so it can avoid the shortcomings of the contact temperature measurement method and has a high temperature upper limit. In addition, non-contact temperature measurement method Thermal inertia Small, up to 1/1000S, so it is convenient to measure the temperature of moving objects and rapidly changing temperatures. Due to the Emissivity The distance between the measured object and the instrument, as well as the influence of smoke, water vapor and other media, this method generally has a large temperature measurement error.

Other measurement methods

According to the different effects of temperature on human body, it can be divided into the following measurement indicators.

Dry bulb temperature

Dry bulb temperature is the current evaluation in China Climatic conditions of the mine One of the indicators of. Features: to a certain extent, it directly reflects the weather conditions of the mine. The indicators are relatively simple and easy to use. However, this indicator only reflects the impact of temperature on mine climate conditions, but does not reflect the comprehensive effect of climate conditions on human heat balance.

Wet bulb temperature

The wet bulb temperature can reflect the impact of air temperature and relative humidity on human thermal balance, which is more reasonable than the dry bulb temperature. However, this index still does not reflect the impact of wind speed on human heat balance.

Equivalent temperature

The equivalent temperature is defined as the enthalpy of wet air and specific heat Ratio of. It is an index to evaluate the mine climate conditions based on energy.

Sympathetic temperature

This index is a calculation chart of sympathetic temperature based on the subjects' feelings of the environment through experiments.

Katado

Catarrh was measured with a catameter. Features: reflects the temperature and wind speed Impact on climate conditions, but does not reflect the impact of air humidity. In order to measure the comprehensive effect of temperature, humidity and wind speed.

Zeroth law of thermodynamics

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thermometer

If two Thermodynamic system If each of them is in thermal equilibrium (at the same temperature) with the third thermodynamic system, they must also be in thermal equilibrium with each other. This conclusion is called“ Zeroth law of thermodynamics ”。 The importance of the zeroth law of thermodynamics lies in its definition of temperature and its measurement method. The thermodynamic system mentioned in the law is composed of a large number of molecules atom An object or system of things. It provides an experimental basis for establishing the concept of temperature.^[4]

This law reflects that Heat balance state All thermodynamic systems in the system have a common macroscopic characteristic, which is determined by the state of these mutually thermal equilibrium systems State function This state function is defined as temperature. And temperature equality is a necessary condition for heat balance.

influence

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Impact on natural environment

The global warming of the earth caused by the uncontrolled emission of human beings to the atmosphere, el nino phenomenon ， Global greenhouse effect At the same time, it also affects the ecological balance of the whole earth and the harmonious development of mankind.

Influence on physical properties

Temperature (° C)	Sound speed (m/s)	Air density (kg/m3)	Acoustic impedance (s/m3)
-10	three hundred and twenty-four point nine	one point three four one	four hundred and thirty-six point five
-5	three hundred and twenty-eight	one point three one six	four hundred and thirty-two point four
zero	three hundred and thirty-one	one point two nine three	four hundred and twenty-eight point three
five	three hundred and thirty-four	one point two six nine	four hundred and twenty-four point five
ten	three hundred and thirty-seven	one point two four seven	four hundred and twenty point seven
fifteen	three hundred and forty	one point two two five	four hundred and seventeen
twenty	three hundred and forty-two point nine	one point two zero four	four hundred and thirteen point five
twenty-five	three hundred and forty-five point eight	one point one eight four	four hundred and ten
thirty	three hundred and forty-eight point seven	one point one six four	four hundred and six point six

Impact on human body

high temperature

Physiologists believe that about 30 ℃ is the best ambient temperature for human body to feel, and also the temperature closest to human skin.^[5]

33 ℃ - sweat glands start to work at this temperature for 2-3 hours, and the human body "air conditioning" - sweat glands start to work, emitting accumulated body temperature through slight sweating.

35 ℃ - The heat dissipation function immediately reacts. At this time, the superficial veins expand, the skin sweats, the heart rate accelerates, and the blood circulation accelerates. For some elderly and infirm people with poor heat dissipation, they need to cooperate with local cooling, or start the indoor air conditioner to reduce the body temperature.

36 ℃ - Level I alarm At this temperature, the human body "cools itself" by evaporating sweat and releasing heat. Sweat, sodium, vitamins and other minerals are excreted every day, and blood volume is reduced accordingly. At this time, drink containing salt, vitamins and minerals should be supplemented in time to prevent Electrolyte disorder At the same time, other cooling measures should also be started.

38 ℃ - The secondary alarm temperature rises to 38 ℃, and it is difficult for sweat glands to ensure normal body temperature. Not only the lungs gasp for breath to exhale heat, but also the heart needs to speed up to output 60% more blood to the body surface than usual to participate in heat dissipation. At this time, cooling measures, heart medication and treatment should not be relaxed.

39 ℃ - The sweat glands of the third level alarm are working hard, which is prone to the risk of sudden heart disease.

40 ℃ - Level IV alarm high temperature has made people dizzy. At this time, people must immediately go to a cool place or use ice to cool down, and those who are unwell need to be sent to the hospital immediately.

41 ℃ - Level 5 alarm: Sweating, breathing, blood circulation... All the organs that can participate in cooling are close to the end of their tether when fully powered. At this time, for the weak and sickly patients and the elderly“ shock Temperature ", be very careful.

42 ℃ - Level 6 alarm The human body is unable to breathe, so ice should be used to cool down. If not, people will die.^[5]

Extreme temperature

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Singular phenomenon

Non metallic materials It can also show magnetism at low temperatures. This kind of magnet is suitable for making new computers storage device Insulation equipment, etc. But such materials will lose their magnetism when the temperature exceeds a certain limit. The non-metallic magnet with the highest critical temperature is about - 230 ℃, which can only be increased to - 208 ℃ even if high pressure is applied.

The low temperature world is like a magician, with wonderful changes in various substances. The air will become a light blue liquid at - 190 ℃. If you put an egg in it, it will produce light blue fluorescence, and it will bounce like a rubber ball when dropped on the ground; When the bright flowers are put in, they will turn into glass and glitter. When they are knocked gently, they will make a "jingle" sound. When they are knocked again, they will break. A goldfish is fished out of the fish tank and lowered head first into the liquid. When the goldfish is taken out again, it will become hard, crystal clear, as if Crystal glass Then put the "glass goldfish" back into the water of the aquarium. Strangely, the goldfish came back to life and swam with its gossamer tail.

Special temperature

-170 ℃: low temperature limit for life survival At this temperature, the simplest microorganisms can survive. Observation shows that, Escherichia coli 、 Typhoid bacillus And suppurative staphylococcus They can survive at - 170 ℃.^[6]

-140 ℃: rubber products processed at low temperature with liquid nitrogen

Rubber products It is very difficult to crush it into fine rubber powder with wide applications. In the world, the industrial production of fine rubber powder from waste tires is mainly adopted liquid nitrogen Low temperature freezing method, that is, rubber is frozen into vitrification If the state is crushed, fine rubber powder can be easily obtained.

Temperature related pictures

-117℃： Alcohol thermometer

The red liquid in the thermometer is alcohol Alcohol will coagulate at - 117 ℃. Therefore, in Antarctica, where the temperature is the lowest on the earth, the alcohol thermometer can also be used. Of course, when the temperature is below - 117 ℃, the alcohol thermometer is useless.

-100 ℃: the coldest compressor

A foreign computer player used more than 4 compressors and made a compressor system that can cool down to minus 100 ℃ to cool the CPU processor!

-89.2 ℃: the lowest temperature on the earth's land

In the interior of Antarctica, people have measured a low temperature of - 89.2 ℃.

-80℃： SARS virus Still alive

A prominent feature of SARS virus is that it is afraid of heat and cold. Even at - 80 ℃, it can survive for at least 4 days, even up to 21 days, while at 56 ℃, the survival time of SARS virus does not exceed 90 minutes.

-70℃： Arctic minimum temperature

Arctic Annual average temperature The annual average temperature in the Arctic is between - 15 ℃ and - 20 ℃, 25 ℃ higher than the annual average temperature in the Antarctic. The polar night period in winter (January) is 180 days, and the minimum temperature is - 70 ℃. Low temperature can prevent some diseases. Eskimo people living in the Arctic mainly eat seal meat and seal oil. Local people rarely have heart disease, cardiovascular disease, hypertension, arthritis and other diseases.

-52.3 ℃: the coldest temperature in China

In China, there are few records of temperatures below - 50 ℃. Inner Mongolia Autonomous Region, China Greater Khingan Range On January 16, 1922, the temperature of - 50.1 ℃ was observed in the Yidu River, which was the lowest temperature recorded before the founding of New China.

After the founding of New China weather station It broke the record for the first time with a low temperature of - 50.7 ℃ on January 20, 1960, and then set a new national record with a temperature of - 51.5 ℃ on January 21, 1960. On the morning of December 27, 1968, Mohe Meteorological Station in Heilongjiang Province, the northernmost meteorological station in China, measured - 50.9 ℃, and on February 13, 1969, Mohe finally gave birth to the record of the extreme minimum temperature in China's existing meteorological data: - 52.3 ℃.

The most fearless flowers in the world are produced in China Saussurea involucrata , even at - 50 ℃, flowers bloom.

0 ℃: water freezing point

70% of the earth's surface is covered by water, about 1.4 billion cubic meters of water, 96.5% of which is seawater, and the rest is fresh water, but more than half of which is ice. So the earth is a planet of water, and it is such a planet that can give birth to life, so "water" is the source of life. With life, there is vitality, and the world will be more wonderful.

Since water can become ice, water can also become Gas diffusion In air. When water freezes at 0 ℃, it loses its fluidity and is no longer a liquid. Therefore, 0 ℃ is called "freezing point of water".

10 ℃: cool and pleasant equator city

In South America Ecuador Capital of China Quito In the city, the equator line just passes through the city. Many people think that cities passing through the equator must be very hot. But this is not the case. No matter in spring, summer, autumn or winter, the monthly average temperature in a year is about 10 ℃, and the annual average temperature difference is only 4 ℃. It is a cool and pleasant equatorial city like spring all the year round.

20 ℃: mycelium growth temperature of Agaricus bisporus

Agaricus bisporus mycelium It can grow at 5 ℃~33 ℃, the suitable growth temperature is 20 ℃~25 ℃, the most suitable growth temperature is 22 ℃~24 ℃, high temperature Lethal temperature 34 ℃~35 ℃.

30℃： mosquito Temperature suitable for survival

Mosquitoes' favorite temperature is about 30 ℃, which is too high to bear. autumn When the climate turns cold and the temperature drops below 10 ℃, they will stop breeding, go into hibernation without eating or moving, and come out again after awakening in the next spring.

40 ℃: temperature limit of human body

Human beings are thermostatic animals, which generally do not exceed the range of 35 ℃~42 ℃. At 41 ℃, human organs such as liver, kidney and brain will have dysfunction. A high fever of 42 ℃ for several consecutive days is enough to kill adults.

50~60 ℃: the hottest temperature on earth

Due to the low cloud cover in desert areas, sunshine Strong, lack of vegetation coverage, and low air humidity, so the temperature rises extremely fast in the daytime, most of the time above 30 ℃, and the temperature can rise to above 50 ℃ at the hottest time at noon. There was a record of 58 ℃ in North Africa (on September 13, 1922 Libya ）。

70 ℃: the most suitable temperature for human taste

Physiological and psychological studies have shown that the various taste sensations people get when eating food are actually the result of the synergistic effect of taste and smell. Some hot drinks, such as coffee, are delicious when the temperature is 70 ℃. Hot milk, hot dishes and bread are most delicious when the temperature is about 70 ℃. Some fried foods, such as fried shrimp, should be kept at about 70 ℃. Although they taste hot, they taste most delicious.

100 ℃: boiling point of water

In a Atmospheric pressure When water is boiling, its temperature is 100 ℃ and can only be maintained at 100 ℃. But when people boil eggs on Mount Qomolangma at an altitude of more than 8000 meters, the highest boiling temperature is only 80 ℃. That is because the pressure is low at a place more than 8000 meters high, so the boiling point of water has only decreased.

200 ℃: underground hot rock power generation

Since 1987 in the UK Magmatic power generation experiment. In a hot rock zone with the highest temperature in the UK, its hot rock at a depth of 6000 meters can heat water to 200 ℃, and then convert the heat energy of 200 ℃ water into electrical energy.

500℃： Concentrated solar cooker

This kind of solar cooker uses parabolic reflector to gather light to obtain higher temperature, and its diameter is generally 1-2 meters. Due to the concentration of energy thermal efficiency High temperature of 500 ℃ can be obtained. This kind of concentrating solar cooker is used in some families in rural China to cook, fry vegetables, boil feed and boil water.

700℃： Cigarette butts mosquito-repellent incense Temperature of

Although the surface temperature of cigarette end is only 250 ℃~300 ℃, the central temperature of cigarette end is generally about 700 ℃~800 ℃, and the burning temperature of mosquito repellent incense is also 700 ℃.

800℃： lava temperature

When a volcano erupts, a large amount of red volcanic lava will be ejected. When it first erupts, it is usually in a liquid state, and the temperature is usually about 800 ℃ - 1000 ℃. During the flowing process of volcanic lava, it continuously heats up the atmosphere and the earth surface, producing a lot of smoke. Therefore, the solidification of volcanic lava during cooling is carried out from outside to inside.

1000℃： Diamonds Formation of

As the saying goes, "Diamond is a lady's best companion". Interestingly, diamonds are pure carbon, and carbon is the fourth most common chemical element in the universe after hydrogen, helium and oxygen. Therefore, the rarity of diamonds does not originate from their chemical elements, but from the method and place of their formation. The diamonds on the earth are believed to be 100 to 300 kilometers deep; The underground with a temperature close to 1000 ℃ was formed and then brought to the ground due to volcanic eruption. From the chemical composition alone, diamonds and graphite used to make pencil lead are actually close relatives. If you put diamonds in a high temperature stove; Then it will only turn into ordinary graphite.

3000 ℃: glass carbon

Glass carbon is a kind of carbon similar to glass, which combines glass and carbon Dual properties of materials. If this substance vacuum Or the working temperature under non oxidizing atmosphere can reach 3000 ℃, and the heat shock resistance is good, which can be used as smelting High purity substance Crucible, Semiconductor epitaxy Furnace induction heating plate is widely used in science.

7000℃： geothermal energy

Geothermal energy is the natural heat energy extracted from the crust. This energy comes from the lava inside the earth and exists in the form of heat. It is the energy that causes volcanic eruptions and earthquakes. The temperature inside the earth is as high as 7000 ℃.

9000℃： Accumulated temperature of rice

Accumulated temperature It is the sum of daily average temperature in a certain period of time. The annual accumulated temperature in southwestern Yunnan, Guangdong, Fujian, Hainan and Taiwan is above 8000 ℃, while Hainan, the southernmost province Ledong County Yinggehai Sanya coastal area, Xisha Yongxing Island The annual accumulated temperature of, Thermal resources It is extremely rich and suitable for the growth of thermophilic crops such as rice. The rice growth in these areas is generally two or even three seasons.

510000000 ℃: the highest temperature created by human beings

The highest temperature that human can produce is 510000000 ℃, about 30 times hotter than the center of the sun, which is the same as that of the United States New Jersey In Princeton Plasma Physics Laboratory Tokamak fusion The reactor was created on May 27, 1994 using a plasma mixture of deuterium and tritium.

1.416833×10^32℃： Planck temperature

Planck temperature is the basis of temperature upper limit ； Modern science believes that it is pointless to speculate that anything is hotter than this. According to the current Physical cosmology This is the universe big bang The temperature of the first instant.

Optimum temperature

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According to the verification of scientists, the optimal living temperature is as follows:

The temperature of the sun bath is 15-30 ℃;

The room temperature shall be kept at 20-25 ℃;

The temperature of bath water is 37-44 ℃;

The temperature of foot washing water is 38-43 ℃;

The temperature of cold water bath is 18-20 ℃;

The temperature of meals is 30-42;

The temperature of drinking water is 30-40 ℃;

The temperature for making tea is 70-80 ℃;

The temperature of bread is 75-99.974 ℃;

The temperature of clothes is 36-60 ℃;

The temperature of clothes must be higher than the body temperature;

The average temperature of the skin is 33 ℃ when the clothing maintains the best comfort.

outer space

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Cosmic temperature

-270.15 ℃: cosmic microwave background radiation

The cosmic microwave background radiation is“ Big Bang ”Left over over all over the universe thermal radiation It reflects the condition of the universe when it was only 380000 years old, and its value is 3K close to absolute zero.

-260℃： Interstellar dust temperature

In cold space, the temperature of interstellar dust can be as low as - 260 ℃.

-250 ℃: low temperature rocket engine

Indian Space Research Organization A cryogenic rocket engine with fuel temperature of - 250 ℃ was successfully tested. Driven by it, the maximum speed of the engine ramjet reaches 40000 rpm, marking that India's space research level has crossed an important milestone.

4000℃： Sunspot Center temperature

We all know that sunspots, when there are more sunspots, will produce geomagnetic storms to bring a lot of inconvenience to people's work. For example, a sailing ship loses its way, communication signals Unable to connect. So sunspots are not really black, and their center temperature is above 4000 ℃. The brightness can still be compared with the light of half a moon in the upper and lower chords. It just looks very dark against the bright light ball.

5000℃： Prominence Basic temperature

The prominence mainly protrudes one of the two edges of the sun Planting the sun Activity phenomenon. They are much weaker than the circular surface of the sun. Generally, they are submerged by the solar halo and cannot be seen directly Total solar eclipse Can only be seen through a telescope. The temperature of the prominence is between 5000 and 8000 ℃, which can spread to hundreds of thousands of kilometers shape all sorts of strange things. Some prominences can exist for a long time. It is strange that the temperature and density of prominence and corona are 800 times different, so scientists are studying how they can coexist for a long time.

1000000℃： Corona temperature

The temperature of the solar corona is as high as 1 million ℃. Russian Academy of Sciences Saint Petersburg University of Technical Physics has successfully developed a thermometer that can measure quickly thermonuclear reactor in Plasma Temperature. The researchers used a laser light source with a special structure in the thermometer, so that the temperature of the plasma with a temperature of up to 1000000 ℃ can be measured instantly.

15000000 ℃: central temperature of the sun

The surface temperature of the sun is 6000 ℃, but the nuclear fusion inside the sun needs extremely high temperature, enough to make any object boil!!! The temperature of plasma is higher

Stellar temperature

-160℃： Mercury Night temperature

Mercury, the closest planet to the sun, has an average distance of 57.9 million kilometers from the sun. It is the closest planet to the sun. Its surface temperature difference is the largest. Because there is no regulation of the atmosphere, the maximum temperature on the sunny side can reach 430 ℃, but the nighttime temperature on the sunny side can drop to - 160 ℃, and the temperature difference between day and night is nearly 600 ℃. This is a world between fire and ice. The temperature change is so great that there is no life on Mercury.

-120℃ Venus Minimum temperature

Venus has the largest temperature difference between day and night, and its daytime temperature can reach 480 ℃; The minimum temperature at night can reach - 120 ℃, so the temperature difference between day and night can reach about 600 ℃.

-60℃： Mars Temperature of

On Mars far from the earth, the average temperature is - 60 ℃.

-150℃： Jupiter surface temperature

Jupiter is the fifth planet in the solar system. Jupiter is the largest planet in the solar system. It can hold 1300 Earths in its interior. Its density is low, and its weight is only 317 times that of the Earth. Jupiter is mostly composed of hydrogen and helium. Jupiter is far from the sun, surface temperature Up to - 150 ℃; The heat emitted from the interior of Jupiter is more than twice that it receives from the sun.

- 240℃： Pluto Minimum temperature

Seen from Pluto, the sun is just a shining light spot. The light and heat it receives from the sun is only one tenth of the tens of thousands that the earth receives from the sun. Therefore, Pluto is a very cold and dark world. The maximum temperature is - 210 ℃, and the minimum temperature is - 240 ℃. Except Pluto Neptune It can also reach - 240 ℃.

Scientists first got a low temperature of - 240 ℃ in the laboratory in 1898, when hydrogen became liquid hydrogen.

- 220℃： Uranus temperature

The "Uranus Day" of one rotation of Uranus is about 17 hours and 14 minutes. Because of its rapid rotation, Uranus, like Jupiter, shows obvious east-west stripes. Because it is far from the sun, Uranian Atmosphere The temperature at the upper end of the cloud is about - 220 ℃, and the surface is light blue.

-210℃： Cetus Dust disk of τ

Tau Cetus is the nearest to the earth except the sun Sun like star , only 12 light years away from the sun, the brightness is about 3.5, which can be seen with the naked eye. It is surrounded by dust The diameter of the dust disk formed with comets is slightly larger than that of the solar system, and the temperature is only about - 210 ℃, which may be caused by the fragments of asteroids and comets colliding with each other.

-200℃： Titan surface temperature

As of 2012, human beings have not found any Extraterrestrial life Evidence of survival. but Cassini Titan, which is being explored, may be a Origin of life Laboratory.

Because its surface temperature is - 200 ℃, Titan is not a place where life can be generated, but its dense atmosphere contains many hydrocarbons. They can produce chemical reactions through the ultraviolet light of the sun. Photochemical reaction Can produce Organic molecule These carbon based compounds are the first step to produce life. But Titan is too cold to take the next step. It is like a deeply frozen earth. In five billion years, it will get the heat needed to produce life, because then the sun will expand into a glowing Red Giant 。 But at that time, as the sun has entered the twilight of life, life has probably been too late to produce.

6000 ℃: solar surface temperature

The surface temperature of the sun reaches 6000 ℃. Solar atmosphere It contains more than 90 chemical elements, and its hydrogen content is the largest, accounting for about Solar mass 71%, helium accounts for about 27%, and other elements account for about 2%, including sodium, calcium, iron, oxygen, etc. Because these chemical elements are produced every day nuclear explosion It emits a lot of light and heat, bringing vitality to people's lives. But the sun's energy is limited. One day, the sun will disappear when it runs out of energy.

A miniature with a mass of 1/1000 of the mass of the moon black hole The temperature is about 6000 ℃, which is equivalent to the surface temperature of the sun.

8000℃： Niulang Star surface temperature

In ancient Chinese legends Niulang Star At night when people watch it, it shines like a gem. In fact, its surface temperature is 2000 ℃ higher than that of the sun, that is, 8000 ℃.

10000℃： Vega temperature

At night, people can watch Vega with Altair at a temperature of 10000 ℃.

100000 ℃: nebula temperature

In the interstellar space, the material distribution is uneven. In some places, cloud gas and dust are relatively dense, forming various cloud objects. These nebulous objects are called nebulae. Annular nebula It's a very famous Planetary nebula Its central star is close to the end of evolution White dwarf The temperature is 100000 ℃ and the density is very high.

10000000℃： neutron star surface

The surface temperature of a neutron star whose mass is equal to that of the sun is about 10 million ℃. The occurrence of nuclear fusion must have a high temperature of more than 10 million degrees Celsius or even hundreds of millions of degrees Celsius.

Absolute temperature

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Absolute temperature scale

thermometer

The ideal and scientific temperature scale based on Carnot cycle takes the freezing point of water (0 ℃) as 273.15K (K is called Kelvin, the unit of absolute temperature scale), and the division of absolute temperature scale is the same as that of Celsius temperature scale.

Absolute zero

Absolute zero, i.e Absolute temperature scale The beginning of is the lowest limit of temperature, which is equivalent to - 273.15 ℃. When this temperature is reached, all atoms and Molecular thermal motion Will stop. The third law of thermodynamics It is pointed out that absolute zero can not be reached through a limited cooling process, so absolute zero is a minimum temperature that can only be approached but cannot be reached.

In 1926, humans achieved a low temperature of 0.71 ° K, 1933 achieved a low temperature of 0.27 ° K, and 1957 created a record of 0.00002 ° K. utilize Nucleus Of Adiabatic demagnetization Method, people have got the distance between Absolute zero The temperature is only 30 millionths of a degree lower, but it is still impossible to get absolute zero.

If there is absolute zero, can it be detected? Is there an instrument for measuring temperature that can measure absolute zero without interfering with the system under test (if the system under test is interfered with, the atoms will move, so it is not absolute zero)? Indeed, absolute zero cannot be measured and is defined by theoretical calculation. It is found that when the temperature decreases, the translational motion of molecules will slow down. Then, according to the extrapolation of experimental data, when the temperature drops to a certain temperature, the translational energy of molecules is zero, so the definition of absolute zero is given.

Although there is a theoretical lower limit of temperature - absolute zero, this does not mean that all movements of matter stop at the temperature of absolute zero. from Statistical thermodynamics From the point of view of, the microscopic motion of matter can generally be divided into molecular translation, molecular rotation, molecular vibration, electronic motion and nuclear motion. stay Absolute zero The molecular translation describing the overall translation of molecules and the molecular rotation describing the rotation of molecules around the center of mass have indeed disappeared, but the molecular vibration, electronic motion and nuclear motion are the lowest quantum state , cannot be frozen by temperature, so the static of the objective world is relative, and the motion is absolute.

Absolute maximum temperature

The energy of particles is expressed through motion. The meaning of absolute zero is that all atoms in the object are still and there is no longer any Thermal movement

So, particles Movement speed The faster the energy is, the higher the temperature of the macro material is. The particles themselves have no temperature and can only express their temperature through energy. Therefore, under a certain pressure, the motion speed of each particle is close to light speed The energy also tends to be infinite, that is, the temperature limit, that is, the absolute maximum temperature.

The relativistic heavy ion collider has a 2.4 mile long circular tunnel. Two beams of colliding particles run in two directions and are accelerated by the coils on the device. Scientists have set six points on the circular tunnel where particle collisions can occur. When the gold nucleus collides head-on, the hot, extremely dense plasma quarks and Gluon Can form, or more accurately, a substance that is similar to a fluid.

According to the staff of Guinness World Records, Brookhaven National Laboratory The relativistic heavy ion collider produced a high temperature of 4 trillion degrees Celsius, 250000 times higher than the core temperature of the sun. Physicists have been able to observe the "nearly perfect liquid" form of matter in the short time of the Big Bang. According to the introduction of Steve Vigdor, a physicist at Brookhaven Laboratory, "absolute zero ratio Quark gluon plasma It is very many orders of magnitude lower, and we are surprised to find that the relativistic heavy ion collider and other science The connection between frontiers and the unification of physics is a very beautiful event. "

At the same time, there is also a research project called the Large Ion Collider Experiment (ALICE) located in the European Nuclear Research Center (CERN). It is one of the five detector experiments of the Large Hadron Collider, and its purpose is also to study the quark gluon plasma (QGP) and other space environmental conditions in the primitive universe. And Large Hadron Collider The difference is, for example, ATLAS detector Compact sub coil (CMS) detector focuses on finding Higgs boson 。 Therefore, large Ion collider There is a fierce competition between the experiment and the relativistic heavy ion collider.

The super high temperature created by the large ion collider experiment also shows that the super machine works well. Despina Hatzifotiadou, a physicist at CERN, believes that the energy density of the Large Ion Collider experiment is three times that of the Large Ion Collider, which can increase the absolute temperature conversion in the super machine by 30%. Therefore, the Large Ion Collider also has a strong collision research capability. The relativistic heavy ion collider is still a winner until at least 2013, because 30% of the scientists have not released the official temperature measurement results.

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